Kinetics of adhesion interaction of polyolefins with metals under conditions of contact thermooxidation. II. Dissolution and diffusion of iron compounds into the bulk of polymer

The kinetics of dissolution and penetration of iron compounds (IC) into the bulk of a polyethylene layer during oxidation in contact with steel as a function of contact temperature and thickness of a polymer layer has been studied by X-ray spectral fluorescence analysis (XSFA). The measured intensity of dissolving species correlates with the rate of contact oxidation. Small amounts of IC dissolve in the absence of oxygen. The depth profiles of IC content were determined by electron probe microanalysis (EPMA). It was observed that the depth of penetration of IC does not exceed 15 mu m up to a contact time of 3.6 ks at a temperature of 473 K. Judging from the value of the effective diffusion coefficient of IC, the process of transfer of IC is diffusion controlled. The results of some model experiments show that the most likely reaction for IC generation is the formation of iron carboxylates by the interaction of iron oxide with the products of contact oxidation of the polymer (carboxyl groups).